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Controlling both conductivity and bandgap chemistry of carbonaceous fillers could broaden up their application potential. However, it has been a difficult synthetic goal for more than a decade. We describe a methodology to do so in a very controlled manner on single-walled carbon nanotubes (SWNT). The approach relies on the extreme extension of a functionalization by 4-nitrobenzenediazoether. We show that the water-soluble Z-diazoether already known to react selectively with metallic m-SWNTs, can also extract electrons from sc-SWNTs. The gradual formation of a covalent aryl bond alters the SWNT electrical conductivity in two steps depending on the functionalization degree. The two consecutive regimes correspond to the grafting of conductor and semiconductor nanotubes. The extent of functionalization was assessed in situ using UV–Vis spectroscopy. The covalent coupling was first evidenced by spectroscopic characterizations of the chemical structure. The consequences on the physical properties of the SWNTs were also measured. The functionalization method reported here brings unprecedented hope for preparing, at large scale, semiconducting SWNTs as excellent-conductivity building blocks for an array of applied semiconductors. This is the first example of the visualization and measurement of optical and electrical properties in function of the progress of nitrophenyl coupling to nanocarbon scaffolds. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: Despite their recognized potential for low cost, flexible and high frequency electronics and photovoltaic, semi-conducting carbon nanotubes (sc-CNTs) did not lead to industrial development yet because they are synthesized as a mixture with metallic carbon nanotubes (m-CNTs). Sorting has been widely studied but cost remains high. Here, the proposed CNT chemical treatment uses diazoether with unprecedented selectivity, avoiding m-CNT and sc-CNT separation. Indeed like conventional diazonium coupling, partly selective for m-CNTs, diazoether coupling induces extinction of nanotube conductivity. The diazoether proved 50times more selective than diazonium as shown by luminescence, Raman spectroscopy and electrical conductivity. Treated CNT solutions containing inactive m-CNTs and highly preserved sc-CNTs were used in transistors with highly increased ON/OFF ratio. Furthermore, the diazoether/CNT reaction was found to follow an unexpected coupling mechanism: a stoichiometric, radical-free reaction instead of a radical chain reaction for diazonium. This drastic change in mechanism, together with a complete description of the reaction kinetics and thermodynamics, brought easy tuning and fine control on the reaction. As a versatile treatment diazoether provides a cheap sc-CNT material for large scale use in printed electronics. [Copyright &y& Elsevier]